In prior art packet switching systems, it is known for each computer system to transmit all of its routing tables to each of the other computer systems once a day. This transmission of routing information occurs at the same time by all of the computer systems, and in general, uses most of the available communication bandwidth during the period of time that the routing information is being exchanged. Normally, the exchange of routing information is done at an off peak time for the packet switching system. This method suffers from the problems of utilizing a large communication bandwidth and transmitting to distant computer systems information that is of little or no value. An additional problem is that each computer system has a large amount of routing data to analyze to determine which of the routing data applies to an individual computer system.
In other prior art packet switching systems, it is known to allow switching nodes to determine their own path through the packet switching system. U.S. Pat. No. 4,081,612 discloses a system where each switching node transmits multiple packets in order to find a route to a destination switching node. This is commonly referred to as broadcast routing. With respect to the broadcast methods used by the packet switching system or any other type of technique which relies solely on the address for finding the destination, these types of methods absorb a large amount of communication bandwidth within the packet switching system as well as place a real time load on each packet switching node.
U.S. Pat. No. 5,377,262 discloses a method of doing routing in distributed switching nodes utilizing the fact that the switching nodes are arranged in a first and second hierarchy. In addition, each switching node maintains routing information based on telephone and switching node numbers. A destination switching node transfers its routing information back to an originating switching node which combines that routing information with its own in order to determine shorter call paths for subsequent call routing. The first hierarchy is a dialing plan hierarchy having groups of switching nodes at each dialing plan level. The second hierarchy is a switching node hierarchy based on switching node numbers of each switching node with at least one switching node of the switching node hierarchy being at a different level in the dialing plan hierarchy. In order to route a call, a switching node first routes through levels of switching nodes in the dialing plan hierarchy until a second switching node is encountered which can determine the identification of the destination switching node based on a dialed telephone number. The second switching node then routes the call through the node hierarchy using the identified node number until a path is determined to the destination switching node. The techniques used in this U.S. Patent suffer from the problem that they are not quick to determine how to utilize new switch nodes that have just been installed in a distributed switch node system and to determine new routes around a failed switch node.